This invention relates to novel interconnect wiring arrangements on a silicon wafer and to methods for producing the same. Mort particularly, the present invention relates to methods for interconnecting a plurality of metal layers on a silicon wafer after transistors and wiring have been patterned and fabricated.
Prior to the present invention, metal layers each positioned on a different vertical height, separated by an insulating layer and positioned on a silicon wafer had been connected by means of relatively high power lasers such as dye lasers utilizing one or more pulses, each a few nanoseconds wide. The laser power is sufficiently high as to effect opening of the top metal layer, usually alumimum, removal of the intermediate silicon-containing layer by microexplosions and migration of metal into the opening through the insulating layer thickness to effect electrical contact between the metal layers. Typically, the laser power utilized is several kilowatts and the width of each pulse is between about 2 and 6 nanoseconds. The major problem with this prior technique for forming interconnections is that the high-powered laser causes microexplosions which, in turn, cause splatter of metal to occur. This results in poor control in forming electrically conductive paths in the desired pattern. In addition, this technique is generally unsuitable for cutting established conductive paths because of this metal splattering which many times creates new undesirable conductive paths. It would be highly desirable to provide a means for interconnecting different metal layers positioned on a silicon wafer in a manner which provides relatively uniform conduction paths without the formation of new undesirable conductive paths. In addition, it would be desirable to provide such means which also is useful for cutting established conductive paths without creating new undesirable conductive paths.